Interfacial microstructure of diffusion bonded joints of TC4 titanium alloy and additive manufactured 17-4 PH stainless steel and effect of process parameters
TC4 titanium alloy and atomic diffusion additive manufactured(ADAM)17-4PH(stainless steel were diffusion bonded with different interlayers at different temperatures.The microstructure characteristics and properties of the joint interface were analyzed by means of optical microscope,scanning electron microscope,EDS analysis and microhardness testing.The results show that a well formed TC4 titanium alloy/ADAM 17-4PH stainless steel diffusion bonded joint is obtained by using a Cu foil+Ni foil composite interlayer at 960 ℃ and 920℃,with holding time of 60 min and welding pressure of 2 MPa.The interfacial area mainly includes four different zones,namely the diffusion affected zone on the TC4 titanium alloy side(DAZ 1),the interface reaction zone(IRZ 1 and IRZ 2)generated by the diffusion reaction of Cu foil+Ni foil and the diffusion affected zone on the ADAM 17-4PH stainless steel side(DAZ 2).When the diffusion bonding temperature is 960 ℃,CuTi+CuTi2 eutectic phase and CuTi2,Ti(Cu,Ni),α-Ti phases are generated in the IRZ 2,with the highest shearing strength of 163 MPa.With the diffusion bonding temperature increases from 920 ℃ to 960 ℃,the width of interface increases from 243.5 μm to 278.2 μm and the maximum microhardness of IRZ 2 decreases from 693 HV0.1 to 612 HV0.1 in the case of Cu foil+Ni foil as interlayers.When the diffusion bonding temperature remains constant(960 ℃),the peak microhardness of the diffusion bonded joint with Cu foil+Ni foil as interlayers is the highest,about 612 HV0.1,while that with Ni foil as interlayer is the lowest,approximately 495 HV0.1,in the IRZ.
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